Fossil fuels are the primary energy source globally, accounting for the majority of total energy consumption. Energy generated from coal-fired thermal power plants remains widely used due to its stability, reliability, and low installation and operating costs. In coal-fired thermal power plants, circulating fluidized bed (CFB) boilers do not require high-quality coal, allowing for the combustion of low-grade coal and biomass. One of the main operational challenges in thermal power plants is the control of the combustion chamber temperature. Controlling the combustion chamber temperature in a CFB boiler is quite complex due to the high delay and nonlinear characteristics caused by the complex interactions between catalyst particles and fuel. In this study, we propose a suitable control method for regulating the combustion chamber temperature in a circulating fluidized bed boiler. This method includes building control loops, identifying the control object, and designing a robust controller for the thermal process. With the robust control method, issues such as high delay and instability in fuel quality are addressed to make the control of the combustion chamber temperature more manageable.